Motorola (well, now Freescale) has several lines of popular microcontrollers, the most accessible of which seems to be the flash-based 68HC908 and/or HCS08 or RS08 (all the same or very similar architectures, with some renaming and assorted minor differences) series. Traditionally, Motorola chips have been very difficult to obtain through low-volume channels (ie to the hobbyist) and Mot hasn't been very good about distinguishing chips you can actually buy vs chips that are so targetted to a particular industry segment that they're essentially unobtainium. But they seem to be catching on. Many can be bought at Digikey, and low-cost development systems are pretty common.
The Freescale xx08 microcontrollers are one of the few microcontrollers with a genuine von Neuman architecture. Peripherals, Flash, and RAM all share the same 64k address space.